Amplitude and intensity

At a rock concert, the engineer decides that the music isn't loud enough. He turns up the amplifiers so that the amplitude of the sound, where you're sitting, increases by 87.0%. By what percentage does the intensity increase? Do not enter unit.

the problem is that you didn't compute the percent by using a percent difference. All of your work is right but you need to use (I1-I2)/I1 = percent difference, use this instead of a straight fraction like you calculated. if you use this equation you will get the desired answer.